1. Technical Field
The present disclosure relates to a centrifugal compressor that compresses a fluid including a gas such as air by using centrifugal force, and a turbocharger.
2. Description of the Related Art
In recent years, various types of research and development have been performed on centrifugal compressors used in turbochargers, gas turbines, industrial pneumatic devices, and the like (see Japanese Patent Laid-Open Publication Nos. 2012-246931, 2012-197749, and 2011-89490).
Centrifugal compressors generally include a housing. This housing has a shroud provided therein. The housing has a wheel provided therein so as to be rotatable around the shaft center thereof. The wheel includes a disk. A hub surface of this disk extends radially outwardly from one side of the turbine wheel in the axial direction. Furthermore, the hub surface of the disk includes a plurality of blades integrally provided at intervals in the circumferential direction. A tip end edge of each of the blades extends along the shroud of the housing.
An introduction flow passage (introduction port) for introducing a fluid into the housing is formed on the inlet side of the wheel in the housing. Furthermore, a ring-shaped diffuser (diffuser flow passage) that decelerates a compressed fluid to increase its pressures is formed on the outlet side of the wheel in the housing. Note that the inlet side and the outlet side mean an upstream side and a downstream side, respectively, when viewed in a flowing direction of a main flow.
A throttle portion is provided between the wheel and the diffuser in the housing. The throttle portion is formed so as to communicate with the diffuser. Furthermore, the width of the flow passage of the throttle portion gradually reduces along the flowing direction of the main flow. A scroll (scrolling flow passage) having a spiral shape is formed on the outlet side of the diffuser in the housing so as to communicate with the diffuser. In addition, a discharge flow passage (discharge port) for discharging the compressed fluid to the outside of the housing is formed at an appropriate position in the housing so as to communicate with the scroll. Note that the discharge flow passage and the winding start side of the scroll are separated by a tongue portion of the housing.